A rupture that occurred on a section of the Mountain Valley Pipeline (MVP) during a May 1 pressure test was caused by a defective fitting manufactured by a third party, a new independent report has found.
The incident caused water and sediment to escape the natural gas pipeline into a nearby stream and wetland. Equitrans Midstream Corp. operates the pipeline and leads the joint venture that owns it.
MVP opponents had pointed to the rupture as evidence that corrosion of the pipeline heightened the risk of gas leaks along the 303-mile pipeline route from northwestern West Virginia to southern Virginia.
The section that failed during hydrostatic pressure testing “involved a manufactured ‘buttwelding’ fitting that mechanically failed before reaching its target test pressure,” said EQT Midstream vice president Justin Trettel in a letter to federal regulators.
He cited the findings of a report carried out by independent assurance and risk management firm DNV.
Trettel explained that, “Fittings are designed following engineering specifications but are not required to be factory pressure tested for reasons of impracticability.”
He added that the rupture “was the project’s only hydrostatic pressure test failure, and it was due to a manufacturer’s defective weld…For MVP, there are more than 2,500 such fittings installed and hydrotested with a single failure resulting in a negligible fitting failure rate.”
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The long-delayed, 2 million Dth/d pipeline began commercial service in June. MVP transports natural gas from the Appalachian Basin to the Southeast United States.
Trettel noted that, “From a manufacturing perspective, the failed fitting had a ‘sister’ fitting in the same test section that was proactively removed from the pipeline and used to provide material for a portion of the mechanical testing aspect of the failure analysis. There were only two fittings with matching pedigree, neither of which remains in the pipeline.”
MVP has faced an onslaught of opposition since its inception, and required an act of congress to gain final approval.
Developing natural gas pipelines out of the Appalachian Basin – the leading U.S. source of natural gas supply – has proven nearly impossible in recent years due to legal challenges from opposition groups.
NGI’s Appalachian Regional Avg. price was $1.480/MMBtu on Tuesday (Sept. 3).
